For starters, why are you running a cable between 2 wireless devices? Have the Airport Express join the extremes network wirelessly. This will then, in effect, double (if not more ) the range of the network you are trying to join. This is what wireless stations like this are designed to do.

Once you have done this, come back and tell us how it works.

Hi,

Sorry if I didn't explain that part well enough, but my understanding from all the various articles/msg boards etc is that by simply 'repeating' or extending the network wirelessly I will effectively be cutting my bandwidth in half as the Airport Express will be taking 50% of the original signal/bandwidth to re-broadcast that out through itself.

This was the original way I set everything up and I really noticed the drop in performance (according to speedtest.net..perhaps not the best test site but alas..when I was near the Extreme I could get anywhere from 20-30Mbps..but from the 'den' and off the 'repeated' signal I would be lucky to see 7-8Mbps.